Turbocharged engines may experience a condition known as “turbo lag” during engine operation. Since the turbocharger is powered by exhaust gas energy, a delay (e.g., turbo lag) may occur in response to a request for increased torque when the turbine and/or compressor are not at speeds at which they may supply sufficient boost pressure to increase the engine torque, such as when the engine is coming out of an idle condition and/or when the exhaust gas is at low temperatures.
In one example, the above mentioned issues may be addressed using a method for controlling an engine in a vehicle, the engine having a turbocharger and a particulate filter upstream of a turbocharger turbine. In one embodiment, the method comprises, under selected boosted operating conditions, injecting a reductant upstream of the filter during an exhaust stroke to generate an exothermic reaction at the filter.
In this way, by including a particulate filter upstream of the turbocharger, turbo lag conditions, if present, may be synergistically addressed during filter regeneration. In one example, when filter regeneration is desired, fuel may be injected into one or more engine cylinders via a late post injection in an exhaust stroke of the engine cycle, to increase the temperature of the exhaust gas before spooling up the turbine. For example, during a boosted engine operation, the late post injection may be used to generate an exothermic reaction at the filter. The energy of the heated exhaust may be used increase turbine speed and reduce turbo lag. At the same time, the heated exhaust may be used to burn off particulates that have accumulated in the filter. The timing and amount of the injection may be controlled based on an amount of heat needed to increase the temperature of the particulate filter for regeneration and/or an amount of heat needed to increase the turbine speed to provide the desired torque.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.